This invention relates to a new technique to induce "tanning" in humans, by utilizing very short, discrete pulses of ultraviolet ("UV") and/or visible light energy of selected wave length, for example about 250-400 nanometers ("nm"), preferably about 280-300 nm with an optimum of about 290 nm.
The prior art discloses several apparati to induce artificial tanning of human skin. See, U.S. Pat. No. 4,862,886 (Clarke); U.S. Pat. No. 4,794,925 (Kei Mori); U.S. Pat. No. 4.711,448 (Tsvi Goldenberg); U.S. Pat. No. 4,611,327 (Clarke;) and U.S. Pat. No. 4,469,102 (Fish). The prior art devices generally utilize a source of continuous fluorescent ultraviolet radiant energy, usually within the Ultraviolet A ("UVA") spectrum (wave length 320 to 390 nm), with very limited amounts of Ultraviolet B ("UVB") spectrum (wave length, 286 to 320 mm); the Ultraviolet C spectrum ("UVC", wave length 40-286 nm) is seldom utilized in tanning machines.
Tanning occurs largely through a process known as melanogenesis, a process which turns skin darker by stimulating the melanin-containing cells known as melanocytes to generate small packets of pigment. When an individual increases the pigment in his or her skin the emotional result is generally a sense of well-being and perceived improved appearance. UVB light is a known initiator for melanogenesis with a peak "tanning efficiency" at a wave length of about 290 nm. However, UVB has heretofore been saddled with safety concerns. This is because, even though it is known that peak tanning efficiency occurs at about 290 nm, it is also true that exposure to UVB energy has a significant risk of the toxic result of erythema, or "sun burn". Because of this risk, Federal Regulations (e.g., 21 CFR .sctn.1040.20(ii)(c)(1)), place strict limitations on the amount of UVB radiation a recipient may be exposed to (usually, the total energy source must emit less than 0.3% UVB). Consequently, prior art tanning devices are ordinarily required to utilize UVA energy sources (e.g., a continuously emitting fluorescent light tube). As a result, currently available tanning booths and the like are required to use the least efficient source of radiant energy to promote tanning.
Light above but near 320 nm is within the UVA spectrum. UVA will induce the so called "immediate tanning" related to the oxidation of pre-existing melanin, the dark pigment within skin. It is thought that this stimulus of tanning is most likely dependent upon the minimal but still present UVB within commercially available tanning light sources. These currently available suntanning light sources use continuous light sources that produce a series of potentially toxic results , for example the rapid destruction of genetic (thymine dimer formation) and protein structure through the build up of cellular toxins, presumably superoxides and resulting products. Such toxic effects are often divided into both short and long term events. The short term events include sun burn, corneal clouding, and retinal damage. The long term effects include premature aging of the skin and accelerated cancer incidence (e.g., melanoma).